Proposed Limpopo West Mine Concept Study ... - SRK Consulting

SRK Consulting: 447493: Limpopo West Geochem Page 36Laboratory analysis undertaken on the core samples included the following:Elemental Composition by total digestion (Aqua Regia);Distilled Water Extract analysed for pH, EC, cations, anions and metals and metalloids by ICP;Acid Base Accounting (ABA) with sulfur speciation;Net Acid Generation;XRD for mineralogical determination;XRF for major elements; andTrace metals / metalloids by quantitative ICP scans.The water sample collected from the Bulk sample test pit located in the central are, taken torepresent shallow aquifer groundwater seepage across the pit, was analysed for the following :Physico-chemical parameters - pH, TDS;Major anions – HCO3, SO 4, Cl; F NO3; and Major cations – Ca, Mg; Na, K.The results of the study can be summarised as follows:The mineralogy results indicated that the samples are dominated by quartz, clay mineralskaolinite and smectite, mica muscovite with the ratio of the minerals being variable in thedifferent lithologies.Acid generating pyrite (FeS 2 ) was observed in the mudstone sample of the overburden and coalseam material with trace amounts detected in the sandstone sample.Acid neutralising minerals are present in all the lithologies analysed with the dominant carbonatemineral being calcite (CaCO 3 ) found in trace amounts in all samples, except sandstone in theinterburden where ankerite (Ca(Fe, Mg, Mn)(CO 3 ) 2 ) was dominant.The ABA results indicated that most of the samples contain low sulfide resulting in low AP, withthe exception of mudstone from the overburden and the coal seam samples. The NPR indicatedthat the mudstone, sandstone and coal lithologies are potentially acid generating, the rest of thelithologies are non acid generating.The NAG test is generally used to confirm ABA results. Table 5-7 presents a summary of theABA and NAG test results. NAG results indicate that the lithologies associated with coal (MST-C, SST, and C) have the potential to generate acidity.The 1:4 solid to liquid ratio distilled water leach test results indicated that the overburdenlithologies seem to mobilise higher concentrations of metals than the interburden lithologies, withaluminium and iron being the only metals that are consistently mobilised at elevatedconcentrations from most of the overburden and interburden lithologies.The Bulk Pit water quality was slightly alkaline. the quality was characterised by high alkalinity,low sulfate concentrations and low concentrations of metals indicating that the water quality ofthe pit lake has not been significantly affected by acid ARD. The ratio of the sum of calcium andmagnesium to sulfate is above 1, indicating that carbonate dissolution is controlling pH.Table 5-7: ABA and NAG test results for the Sasol Mafutha Geochemical AssessmentWaste TypeOverburdenInterburdenLithologyCONSANMST-CMSTMST-CMSTMST-SID- CSHPIR-CSHSSTCSHABAassessmentNAGassessmentCommentHi pH/ S’fide ND/ Hi NPRS’fide ND/ Lo NPRLo S’fide/ Hi NPRS’fide dominates/ Lo NPRLo S’fide but NP NDRelatively Hi S’fide / Hi NPRHi pH/ Lo Sulfide/ Hi NPRHi pH/ Lo S’fide/ Hi NPRHi pH/ S’fide ND/ Hi NPRLo pH/ S’fide present/Marginal NPRDecisionGOGP/LAKJ Report_April2013_19April2013 (1)_Final_Ludi_22052013 April 2013